Miniaturizing semiconductor dice has been an increasing trend for various functions. The miniaturized semiconductor dice is increasingly provided with more and more input/output (I/O) pads within a smaller region, so the density of metal pins are increased. Thus, the package technology of lead frames has been replaced by the technology of, for example, ball grid arrays (BGAs).
Advantages of BGAs include a compact form, increased density, and an arrangement allowing solder connections that are less subject to damage and distortion. With a variety of integrated circuit-based products in fashion, such as cell phones, personal data assistants, and MP3 players, the products are typically equipped with at least one systemic chip within a smaller volume.
A wafer level package (WLP) has been developed to package a wafer prior to sawing (i.e., dicing). For example, U.S. Pat. No. 5,323,051 discloses one type of wafer level package. However, for WLP, the increasing numbers of bonding pads, coupled with commensurate reduced pitches, would result in signal coupling and noise. In addition, the reliability of the package may be reduced because of the reduced pitches. Thus, WLP may not satisfy the needs of smaller dice fabricated with smaller design rules.
In an attempt to resolve the issue, U.S. Pat. No. 7,196,408 discloses a method relating to the semiconductor packaging process. A plurality of good dice, after testing and sawing, is rearranged on another substrate for a sequential packaging process. The plurality of rearranged dices has wider pitches for suitable distribution of bonding pads thereon, such as using a fan-out technology. Such a method attempts to resolve the issues of signal coupling and noise caused by small pitches.
However, for the semiconductor chip with smaller and thinner packaging structures, prior to the wafer sawing, the wafer may be processed by a thinning process, such as the wafer is to be thinned in the thickness of 2 to 20 mils (i.e., 50 .mu.m to 500 .mu.m) by backside lapping. Then the wafer is sawn thus becoming individual dice. The thinned dices are rearranged on another substrate. Then, a molding process is applied on the thinned dice to form a molding structure. Because both the dice and the molding structure are greatly thinned, the stress from the molding structure itself causes warpage after the substrate is separated from the molding structure. The warpage of the molding structure may make a subsequent sawing process difficult. Accordingly, what is needed is a packaging method for die rearrangement that efficiently resolves the issue of warpage in a molding package.